Method of making multi-ply door core, multi-ply door core, and door manufactured therewith

ABSTRACT

The present invention concerns a method of forming a multi-ply core component. A mold press is provided having an upper die and a lower die defining a mold cavity. At least one of the upper die and the lower die has a plurality of protrusions. A first wood composite board and a second wood composite board are disposed within the mold cavity. The first and second boards are fused proximate the plurality of protrusions by compressing the boards in the mold cavity through application of heat and pressure.

FIELD OF THE INVENTION

The present invention is directed to a method of forming a multi-plycore component. The disclosed method comprises the steps of: providing amold press having an upper die and a lower die defining a mold cavity,at least one of the upper die and the lower die having a plurality ofprotrusions; disposing a first wood composite board and a second woodcomposite board within the mold cavity; and fusing the first and secondboards proximate the plurality of protrusions by compressing the firstand second boards in the mold cavity through application of heat andpressure. The present invention is also directed to the resultingmulti-ply core component formed by practice of the method, and a doorcomprising the core component.

BACKGROUND OF THE INVENTION

Man-made boards, such as fiberboard, can be embossed or molded to havethree-dimensional shapes and various design and structural featuresfound in natural wood. Types of useful man-made boards including: (a)fiberboards such as hardboard (e.g., low-density hardboard), soft board,and medium-density fiberboard and (b) chipboards such as particleboard,medium-density particleboard, and oriented strandboard (“OSB”).Composites of these boards are also useful. Such boards, particularlyhardboard, have found widespread use in the manufacture of doorskins.

Commonly, doorskins (also referred to as door facings) are molded from aplanar cellulosic mat to include one or more interior depressions orcontours, such as one or more square or rectangular depressions that donot extend to the outer edge or periphery of the doorskin product.Doorskins often require inclined molded walls having a plurality ofcontours that include varied curved and planar surfaces. Where thedepressions or contours are included on a doorskin product, this canserve to replicate a more expensive natural wood paneled door. Forexample, door skins having two, three, four, five, and six panel designsare commonly produced. The exterior or visible surfaces of thefiberboard also can be embossed with a design simulating a wood grainpattern such as found in a natural piece of wood.

A hollow core door typically includes a peripheral frame, and two doorskins having exterior surfaces and interior surfaces secured to oppositesides of the frame using an adhesive binder. The binder is placed atleast at the contact points along the periphery of the door assembly.Because the door skins are contoured, and because of the width of theframe, an open interior or hollow space of varying dimensions is formedbetween the spaced door skins.

A door having such an open interior may not have the characteristics ofa natural solid wood door, because the interior spaces defined by thedoor skins will be hollow or empty. The hollow spaces cause the door tobe lighter than may be preferred. Further, the sound insulation providedby such doors may not be satisfactory in particular installations. Acore material (e.g., core pieces or components) is sometimes used tofill these hollow spaces. Such a door may be known as a hollow coredoor.

Conventional core materials for use in hollow core doors includecorrugated cardboard and paper. However, such materials may not provideadequate sound insulation. In addition, they may not provide the doorwith the desired weight, for example the weight of a similarly-stylednatural solid wood door.

Other conventional core materials include wood composite materials, suchas composite softboard. Such door cores are suitable for someapplications, such as doors requiring relatively thin door cores havinga thickness of 0.375 inches or less. However, standard exteriorresidential door cores are 1.125 inches thick (for a 1.375 inch thickdoor). Standard exterior commercial door cores are typically 1.50 inchesthick (for a 1.750 inch thick door). The manufacture of conventionaldoor cores using prior techniques have not been cost effective for doorcores having a thickness or caliper of 1.00 inch or greater.

Generally, conventional techniques for providing a thicker door coresuitable for exterior residential and commercial door use involve eitherlaminating two or more thinner boards using a synthetic resin or moldinga single core. Neither of these techniques provides an inexpensive, costeffective core product for all core requirements.

Techniques involving laminating two or three relatively thin, woodcomposite boards using a synthetic adhesive, such as casein or polyvinylacetate, are expensive and inefficient. The adhesive increasesmanufacturing costs. In some cases, manufacturing costs for producing acore component having a caliper of 1.00 inch or more have been costprohibitive when adhesives are used. Therefore, such methods are notdesirable for door core manufacturers, or result in an expensive doorfor consumers.

Techniques involving molding a mat of material to the desiredconfiguration and caliper of 1.00 inch or greater also fail to provide acost effective alternative. Many doors include a door core componenthaving a density of between about 10 lb/ft³ to about 30 lb/ft³. Whenforming a one-piece core component in that density range, having athickness of more than 1.00 inch, it is difficult to successfully drythe core material thoroughly without burning the surfaces. In addition,manufacturing costs are increased due to the amount of press time andpress temperature required, as well as the amount of material needed toform the core.

Therefore, there is a need for a door core component having a thicknessof 1.00 inch or greater that is cost effective to manufacture, and thathas insulation and weight characteristics desirable to consumers.

SUMMARY OF THE INVENTION

The present invention relates to a method of forming a multi-ply corecomponent. A mold press is provided having an upper die and a lower diedefining a mold cavity. At least one of the upper die and the lower diehas a plurality of protrusions. A first wood composite board and asecond wood composite board are disposed within the mold cavity. Thefirst and second boards are fused proximate the plurality of protrusionsby compressing the first and second boards in the mold cavity throughapplication of heat and pressure.

The present invention also concerns a multi-ply wood composite corecomponent. The core component has at least first and second fused plies.The fused plies have first portions at a first density and secondportions at a second density greater than the first density. The pliesare fused together at the second portions.

A door comprises a peripheral frame having opposing sides, first andsecond door skins, and a wood composite core component. Each of theskins has an exterior surface and an interior surface secured to one ofthe sides of the frame. The core component is disposed between theinterior surfaces of the skins. The core component has at least firstand second fused plies, and has first portions at a first density andsecond portions at a second density. The second density is greater thanthe first density. The plies are fused together at the second portions.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a fragmentary perspective view of a mold press according tothe present invention;

FIG. 2 is an elevational view of the mold press of FIG. 1;

FIG. 3 is an elevational view of a core component according to thepresent invention;

FIG. 4 is an elevational view of a core component;

FIG. 5 is a fragmentary perspective view partially in section takenalong line 5-5 of FIG. 4 and viewed in the direction of the arrows;

FIG. 6 is a perspective view partially in section of a door having acore component according to the present invention;

FIG. 7 is an elevational view of a universal core component according tothe present invention;

FIG. 8 is an elevational view of a universal core component according toa second configuration; and

FIG. 9 is an elevational view of a core component according to a secondembodiment.

DETAILED DESCRIPTION OF THE INVENTION

As best shown in FIG. 1, mold press 10 comprises an upper mold die 12and a lower mold die 14 defining therebetween a mold cavity 16. Upperdie 12 includes planar portions 18 and a plurality of protrusions 20.Protrusions 20 preferably include outer planar portions 22 and sidewalls24 extending from and integral with outer planar portions 22 and planarportions 18. Sidewalls 24 extend angularly from planar portions 18 toouter planar portions 22 in the range of about 20° to about 80°,preferably from about 30° to about 50°. Similarly, lower die 14preferably includes planar portions 18 a and a plurality of protrusions20 a. Protrusions 20 a also include outer planar portions 22 a andsidewalls 24 a. Protrusions 20 a on lower die 14 are aligned withprotrusions 20 on upper die. Specifically, planar portions 18 and 18 a,and outer planar portions 22 and 22 a, are preferably aligned andparallel to each other, respectively. Protrusions 20 and 20 a aredisposed adjacent each other in order to apply the required forces toachieve the results of the invention.

As best shown in FIG. 2, at least a first board B1 and a second board B2are disposed between upper and lower dies 12, 14. Preferably, boards B1,B2 each have an initial thickness of at least about 0.50 inches to about1.00 inch, more preferably between about 0.70 inches to about 0.80inches, an initial density of between about 10 lb/ft³ to about 25lb/ft³, more preferably about 15 lb/ft³, and an initial moisture contentof about 6.5% by weight. Boards B1, B2 are preferably low densityboards, such as softboard or insulation board. Preferably, boards B1, B2do not contain any synthetic resin. Rather, the wood fibers in boardsB1, B2 are held together by the natural wood binder lignin, as known inthe art. However, it should be understood that wood composite boardscontaining synthetic resin, or even tongue oil, may also be used in thepresent invention. However, such boards are generally more expensivethan resin-free boards.

Boards B1, B2 are compressed in mold press 10 using heat and pressure,as known in the art. Preferably, mold cavity 16 has a temperature ofabout 400° F. to about 500° F. more preferably about 450° F. Pressure isincreasingly applied to boards B1, B2 during compression, until amaximum desired pressure is achieved. Preferably, the press pressure isin the range of about 400 pounds per square inch (psi) to about 850 psi,more preferably in the range of about 600 psi to about 800 psi. Afterthe maximum pressure is achieved, it is sustained for a selected periodof time in order to fuse boards B1, B2 together. This hold time at whichmaximum pressure is sustained is preferably about five minutes. However,the hold time may be as short as about 150 seconds, depending on thetemperature of mold cavity 16, the press pressure, and moisture contentof the boards being fused.

Applicants have discovered that wood fibers from boards B1, B2 aresufficiently fused together during the compression operation withoutrequiring the use of an additional adhesive. The natural lignin in thewood fibers of boards B1, B2 is fused together in portions compressed byprotrusions 20, 20 a. As best shown in FIG. 3, a multi-ply corecomponent 26 is formed having an inverse configuration of mold cavity16. Core component 26 comprises a first ply 28, a second ply 30, andfused portions 32. First and second plies 28, 30 form low densityportions 34 having a thickness of between about 1.00 inch to about 2.00inches, more preferably between about 1.125 inches to about 1.50 inches,and having a specific gravity of about 1.10 or less, preferably aspecific gravity of about 1.00 or less. By contrast, fused portions 32have a thickness of between about 0.25 inches to about 0.50 inches, anda relatively high density with a specific gravity of at least about1.20, preferably at least about 1.30. Due to the angles of sidewalls 24,24 a, there is a density differential between fused portions 32 and lowdensity portions 34.

The ability to adequately fuse boards B1, B2 together, and the resultinghigh density of fused portions 32, is achieved through the focusedconcentration of heat and pressure between converging protrusions 20, 20a during compression. On the other hand, relatively low heat andpressure is applied to low density portions 34 due to the configurationof mold cavity 16. Boards B1, B2 preferably undergo only minimal or nocompressive forces in low density portions 34. In this way, the fullthickness of boards B1, B2 is maintained in low density portions 34 ofcore component 26. The preferred thickness of low density portions 34 ispreferably about 1.125 inches or 1.50 inches, depending on whether thecore component is to be used in a residential or commercial door,respectively. If any compression does occur in low density portions 34,generally the thickness of portions 34 is unaffected, or the wood fibers“spring back” to their initial thickness after the compression process.

Plies 28, 30 are fused together and form a single core component 26having a variable density. As best shown in FIGS. 4 and 5, corecomponent 26 includes a first major surface 36, an opposing second majorsurface 38, and edges 40. Core component 26 also includes a firstplurality of channels 42 extending inwardly into core component 26relative to first major surface 36, and a second plurality of channels42 a extending inwardly into core component 26 relative to second majorsurface 38. Each of the first plurality of channels 42 includes a bottom44 and sides 46 extending angularly from and integral with bottom 44 andfirst major surface 36. Likewise, each of second plurality of channels42 a includes a bottom 44 a and sides 46 a extending angularly from andintegral with bottom 44 a and second major surface 38.

Fused portions 32 are formed between channels 42, 42 a. As well known inthe art, the density of a wood composite substrate increases as thecaliper or thickness decreases during a compressive operation if thesubstrate has an initial thickness and density that is substantiallyuniform. Therefore, core component 26 has the highest density betweenbottoms 44, 44 a of channels 42, 42 a. Because of the configuration ofprotrusions 20, 20 a, core component 26 exhibits a gradually decreasingdensity in transition portions 48 formed between sides 46, 46 a. Lowdensity portions 34 have the lowest density of any portion of corecomponent 26. Transition portions 48 have a density that graduallyincreases from a density substantially equal to low density portions 34in areas adjacent low density portions 34, to a density substantiallyequal to the density of fused portions 32 in areas adjacent fusedportions 32.

Density variations between low density portions 34, fused portions 32and transition portions 48 are created by the configuration of moldcavity 16, and the compressive forces acting on boards B1, B2. Duringthe compression operation, force is applied when protrusions 20, 20 aare pressed into boards B1, B2. This applied force is perpendicular tothe surfaces of boards B1, B2, thereby compressing boards B1, B2 to formchannels 42, 42 a of core component 26. In addition, as protrusions 20,20 a are pressed into boards B1, B2, the applied force also createsinternal forces within and between the wood fibers, which generateforces away from the applied force created by protrusions 20, 20 a. Asboards B1, B2 are squeezed together during the compression operation,compressive forces disrupt the lignin in wood fibers between protrusions20, 20 a. The wood fibers and lignin are reconfigured and fused togetherto form fused portions 32.

The internal forces of the fibers in boards B1, B2 extend perpendicularto the applied force from protrusions 20, 20 a. As the applied forcefrom protrusions 20, 20 a increases, the outwardly extending internalforces are also increased, creating a force that flares out fromprotrusions 20, 20 a. However, protrusions 20, 20 a are spaced toprovide low density portions 34 between adjacent, high densitycompression areas (forming fused portions 32). This provides for thevariable density of core component 26 (i.e. high density of fusedportions 32, a low density of low density portions 34, and transitionaldensity portions 48). Transition portions 48 and low density portions 34provide an area for dissipation of the compressive and internal forcescreated in fused portions 32.

In this way, additional pressure may be applied to fused portions 32,thereby increasing the density of fused portions 32 even more.Specifically, steam is created in the wood fiber material duringcompression operations due to the applied heat and pressure. By allowingthis steam to escape, pressure is decreased. The steam created duringthe compression operation migrates from areas of high pressure (i.e.fused portions 32) to areas of low pressure (i.e. low density portions34). In this way, the compression of fused portions 32 may be maximized,since pressure may be increased or maintained in these areas, creatingthinner, more highly compressed areas. Previously, the effects ofcompressive and internal forces limited the achievable density of woodcomposite boards. Conventional wood composite boards typically have aspecific gravity of about 1.00 or less. Attempts to achieve boardshaving higher densities often resulted in blow-out or collapse of thesubstrate due to the effects of such forces. In the present invention,fused portions 32 of core component 26 may be compressed to a muchhigher density than previously achievable, having a specific gravity of1.20 or even 1.30 or higher, thereby overcoming the prior limitationscaused by compressive and internal forces. Such densities are possibledue to the configuration of mold cavity 16, wherein high compressive andinternal forces may be dissipated in low density portions 34.

Transition portions 48 have a gradually decreasing density due to thegradually dissipating internal and compressive forces, which migrateoutwardly from the applied compressive forces of protrusions 20, 20 a.Thus, internal forces due to compression create a compression zone (i.e.transition portions 48) that spreads out from a point of applied force(i.e. protrusions 20, 20 a), a phenomenon not unlike that found in soilmechanics.

Most of the compressive force applied by protrusions 20, 20 a of moldpress 10 is concentrated in areas forming fused portions 32. Fusedportions 32 comprise a relatively small surface area of core component26, relative to first and second major surfaces 36, 38. For example, asbest shown in FIG. 4, first major surface 36 of core component includesrecessed channels 42, formed by protrusions 20 as described above.Second major surface 38 (shown in FIG. 5), includes a correspondingpattern of channels 42 a that are aligned with channels 42. Only fusedportions 32 defined by these channels 42, 42 a are high density areas.It is apparent from FIG. 4 that a majority of the surface area of majorsurface 36 comprises low density portions 34. Thus, a majority of corecomponent 26 has a relatively low specific gravity defined by lowdensity portions 34. In this way, compressive forces may be concentratedin relatively small areas of core component 26 during formation, withample low density portions 34 for dissipating internal forces createdtherefrom.

It should be noted that various configurations of protrusions 20, 20 amay be used, so long as sufficient fused portions 32 are formed toadjoin boards B1, B2 together. The bond achieved need not be overlystrong, because core component 26 is to be used as an internal door coreor other internal core, such as a core for use with wainscot. Oncepositioned within the hollow space between the door skins, corecomponent 26 is not likely to delaminate. Boards B1, B2 are sufficientlyfused to permit handling during manufacture without delaminating.

For example, a door 50 is best shown in FIG. 6 including core component26. Door 50 includes a peripheral frame 52 formed of wood stiles andrails, and having opposing sides. First and second door skins 54, 56 areadhesively secured to frame 52. Each of skins 54, 56 has an interiorlydisposed surface that is secured to opposing sides of frame 52, as wellknown in the art. Core component 26 is disposed between skins 54 and 56.Core component 26 may be secured to frame 52 or skins 54, 56 using anadhesive, though use of such an adhesive is not necessary. Corecomponent 26 may be configured to have channels 42, 42 a (as describedabove) that correspond to the configuration of molded skins 54, 56.Molded skins 54, 56 may be configured to simulate door facings having aplurality of panels, as known in the art.

It should be understood that core component 26 may be configured tocorrespond to various door configurations. For example, a universal corecomponent 60A may be used that can accommodate different styles ofmolded door skins, as best shown in FIG. 7. Core component 60A includesa first major surface 62A and channels 64A recessed from first majorsurface 62A. The opposite side of core component 60A also includeschannels (not shown) aligned with channels 64A. As described above,fused portions are formed between channels 64A and the channels on theopposing side of core component 60A. Core component 60A has the sameconfiguration as described above for core component 26, except thatchannels 64A form a different pattern compared to channels 42 in corecomponent 26. Thus, any configuration of channels may be formed intocore component 60A (or 26), as long as a sufficient portion defines lowdensity portions (i.e. first major surface 62A).

As best shown in FIG. 8, another configuration for a universal component60B is provided, which may also be used for various door configurations.Core component 60B includes a first major surface 62B and channels 64B,as described above. However, channels 64B have a different configurationcompared to channels 64A (or channels 42). In addition, channels 64B arerelatively wide compared to channels 64A. As such, the fused portions incore component 60B are also relatively wide. Thus, channels 64B may havevarying widths, so long as there are sufficient low density portions(i.e. first major surface 62B) to permit internal forces fromdissipating during the compression process and formation of the fusedportions.

In a second embodiment of the present invention, three or more boardsare fused together. For example, as best shown in FIG. 9, core component70 comprises a first ply 72, a second ply 74, a third ply 76 and fusedportions 78. Core component 70 is formed by compressing three boardstogether using the same process described above. Plies 72, 74, 76 formlow density portions 80 having a specific gravity of about 1.10 or less,preferably 1.00 or less. Fused portions 78 have a higher density, asdescribed above for core component 10, having a specific gravity of atleast about 1.20, preferably at least about 1.30.

Preferably, boards used to form core component 70 each have a thicknessof between about 0.375 inches to about 0.667 inches. As such, the totalcombined thickness of low density portions 80 of core component 70 isbetween about 1.125 inches to about 1.50 inches. Fused portions 78 havea thickness of between about 0.25 inches to about 0.50 inches. A corecomponent having four plies may even be achieved using the same process,wherein four thinner boards are fused together.

The present invention provides a method of manufacturing a corecomponent that is cost effective and provides insulation and weightcharacteristics desired for a door. By eliminating the need for anadhesive, the core component disclosed herein is substantially cheaperto manufacture compared to conventional door cores. The disclosed methodallows for the production of two or more thinner, easily dried pliesthat may then be laminated together without the use of an additionaladhesive.

It will be apparent to one of ordinary skill in the art that variousmodifications and variations may be made in configuration orconstruction of the present invention without departing from the scopeor spirit of the invention. For example, initial density, thickness andmoisture content of the boards being fused, as well as presstemperature, press time and die pattern, are interrelated variables thatmay differ depending on the particular boards being fused as well as thedesired configuration and application of the resulting core component.It is intended that the present invention cover all such modificationsand variations, provided they come within the scope of the followingclaims and their equivalents.

1. A method of forming a multi-ply core component, comprising the stepsof: providing a mold press having an upper die and a lower die defininga mold cavity, at least one of the upper die and the lower die having aplurality of protrusions; disposing a first wood composite board and asecond wood composite board within the mold cavity; and fusing the firstand second boards proximate the plurality of protrusions by compressingthe first and second boards in the mold cavity through application ofheat and a pressure of about 400 to about 850 psi and forminghigh-density portions proximate the plurality of protrusions andlow-density portions adjacent the high-density portions, wherein thefirst and second boards are fused in the high-density portions.
 2. Themethod of claim 1, including the step of providing as the first andsecond boards one of insulation board and softboard.
 3. The method ofclaim 2, including the step of providing as the first and second boardsinsulation boards having an initial thickness of between about 0.70 inchto about 0.80 inch.
 4. The method of claim 3, including the step ofproviding insulation boards that are resin-free.
 5. The method of claim1, including the step of compressing the boards by application of amaximum pressure sustained for a predetermined period during saidcompressing step.
 6. The method of claim 5, including the step ofapplying the maximum pressure for at least about 150 seconds.
 7. Themethod of claim 6, including the step of applying the maximum pressurefor about five minutes.
 8. The method of claim 1, including the step offorming channels in the first and second boards, each of the channelshaving a bottom and side walls extending from and integral with thebottom and an outer planar surface.
 9. The method of claim 1, includingthe step of compressing the first and second boards sufficiently toachieve high-density portions having a specific gravity of at leastabout 1.30.
 10. The method of claim 1, including the step of compressingthe first and second boards sufficiently to achieve high densityportions having a thickness of at least about 0.25 inch.
 11. The methodof claim 1, including the step of compressing the first and secondboards sufficiently to achieve low density portions having a thicknessof at least about 1.00 inch.
 12. The method of claim 1, including thesteps of: providing the upper die with a first plurality of protrusions;providing the lower die with a second plurality of protrusions; andaligning the first plurality of protrusions with the second plurality ofprotrusions.
 13. The method of claim 1, wherein the first and secondboards are fused proximate the plurality of protrusions by compressingthe first and second boards in the mold cavity through the applicationof heat and a pressure of about 600 to about 800 psi.